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| PWM / Relay Motor control circuit: |
| This circuit uses pulse width modulation to control the speed of a DC motor and two single pole relays to control clockwise or counter clockwise motor rotation. A 555 astable oscillator supplies squarewave pulses to a TO220 power(TIP31A) transistor,which rapidly switches power to the motor. Diodes are used to shunt voltage spikes from the relay coils and prevent them from entering the control and supply lines. A 0.1uF capacitor is used to dampen motor transients. |